Implantable biomedical devices are gaining widespread acceptance in the medical industry, and are finding increasing applicability as permanent solutions to medical problems. What at one time represented last-resort options in treating medical maladies such as defective or diseased coronary valves in the human vasculature have now become primary care procedures. The success of implantable medical devices, and particularly prosthetic devices in coronary-related procedures has lead to research and implementation of other applications of implantable prosthetic medical devices for addressing a wide variety of medical issues.
As medical device implantation procedures become more commonplace, and physicians' confidence in the long-term reliability of such implanted devices expands, such medical devices are being implanted in patients who are expected to live many years subsequent to the implantation procedure. Accordingly, an ever-increasing pool of prospective patients is being created as candidates for medical device implantation. As a result, the implanted medical devices are being expected to operate properly for an extended period of time.
An issue that arises as such medical devices are being utilized in vivo for relatively long periods of time is the biological effects on the performance of such devices. In particular, the formation of deposits such as coagulative blood components and/or blood-borne minerals on blood-contacting surfaces of the implanted medical devices is a major source of performance diminishment and/or device failure.
A particular example of such biological effects on an implanted medical device is in the specific application of implanted replacement heart valves. Build-up of coagulative blood and/or mineral deposits on such implanted heart valves, and particularly at the valve leaflets thereof, reduce the effectiveness of the heart valves, and may even lead to operational failure thereof.
In the case of mechanical heart valves, implanted device recipients must take anti-coagulation drugs for the remainder of their lives from the time that the device is implanted in order to prevent build-up on respective surfaces of the implanted device. Not only is such a practice inconvenient and expensive, it may also present dangers to the patient wherein the healthy coagulative properties of the patient's blood are suppressed. Such suppression of the normal properties of the patient's blood can lead to excessive bleeding as a result of internal or external injury.
Some systems developed to date utilize electrical energy applied to the implanted medical device to eliminate and otherwise thwart the formation of mineral deposits on respective surfaces thereof. The systems proposed to date, however, utilize electrodes placed on or adjacent to the treatment area (often times the heart, or portions thereof) that are configured to produce an electric charge at the targeted therapy location to minimize or eliminate blood component deposits formed thereon. Because the electrical energy intensity required in achieving such a result is more than nominal, great caution must be taken in order to avoid electrical interference with the normal operation of the heart. Accordingly, many known systems utilize complex sensing and timing arrangements for applying electrical energy to a targeted therapy location only during non-critical periods of the heart beat. In addition, such systems require the positioning of the associated electrodes at locations adjacent to the therapeutic target, which typically means positioning such electrodes at or within certain ventricles of the heart. The electrode implantation procedure alone, therefore, presents its own dangers to the patient.
It is therefore a principal object of the present invention to provide an implantable apparatus which develops and focuses electrical current at an implanted medical device for the minimization and/or elimination of the blood component deposits thereon without having to position current-transmitting electrodes at sensitive regions within the patient's heart.
It is a further object of the preset invention to provide a system for minimizing and/or eliminating deposits on respective blood-contacting surfaces of implanted bio-medical devices by focusing sub-threshold electrical current at electrically conductive portions of the implanted medical device.